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A072531
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Number of primes p such that n divided by p leaves a 1 or a composite (nonzero) remainder.
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7
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0, 0, 1, 1, 1, 1, 2, 1, 2, 1, 3, 1, 3, 2, 3, 2, 3, 2, 5, 3, 5, 3, 5, 2, 6, 3, 6, 3, 6, 3, 7, 6, 5, 6, 7, 3, 7, 5, 8, 4, 8, 4, 10, 6, 8, 7, 9, 6, 10, 7, 9, 8, 11, 6, 11, 9, 10, 7, 11, 5, 14, 9, 11, 9, 11, 8, 15, 9, 13, 8, 14, 8, 14, 12, 14, 11, 15, 9, 15, 11, 14, 12, 18, 10, 16, 14, 15, 13, 16, 9
(list; graph; refs; listen; history; internal format)
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OFFSET
| 1,7
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EXAMPLE
| a(7) = 2: there are 2 primes viz. 2,3 which leave a remainder 1 on dividing 7.
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MATHEMATICA
| Table[Count[PrimeQ[DeleteCases[Table[Mod[w, Prime[j]], {j, 1, PrimePi[w]}], 0]], False], {w, 1, 256}]
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CROSSREFS
| Cf. A072530.
Sequence in context: A029238 A126131 A138012 * A025818 A079413 A027351
Adjacent sequences: A072528 A072529 A072530 * A072532 A072533 A072534
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KEYWORD
| nonn
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AUTHOR
| Amarnath Murthy (amarnath_murthy(AT)yahoo.com), Aug 01 2002
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EXTENSIONS
| More terms from Labos E. (labos(AT)ana.sote.hu), Aug 02 2002
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